GB573046A - Improvements in or relating to the separation of butadiene from olefines - Google Patents

Abstract

Butadiene is separated from a C4 fraction containing unsaturated hydrocarbons by contact in an absorption column, at 0-50 DEG C. and a pressure insufficient to cause liquefaction, with such an amount of an aqueous solution containing a cuprous salt and a hydroxy-alkylamine that, when not less than 93.5 per cent by volume of the butadiene is contained in the solution withdrawn from the column, the vapour pressure of the butadiene over the solution in the base of the column is equal to at least 65 per cent of the operating pressure, part of the gases being disengaged from the solution in the base of the column and used to strip dissolved butenes from the descending solution. Gas mixtures containing, in addition to butadiene and butenes, other hydrocarbons and inert substances may be treated. The dissolved butadiene is recovered by the application of heat and/or reduced pressure. The absorbing solution preferably contains also the hydrochloride of the hydroxy-alkylamine in an amount equal to 1 mol. per atom of copper. Acetylene must first be removed from gas mixtures to be treated. If their oxygen content is less than 0.1 per cent by volume, the solution may be retained in its reduced state by the presence of metallic copper or by heating with copper to 15-105 DEG C. In an example, a gas 50 per cent each butadiene and butenes is passed at atmospheric temperature and pressure into a packed column at its mid-point, an aqueous solution of cuprous chloride, monoethanolamine and hydrochloric acid being pumped in at the top. The solution is heated to 45 DEG C. in the base, and the amount used is such as to give a partial pressure of butadiene of .65 atm. The solution is removed and heated to 105 DEG C. yielding a gas which is 95 per cent butadiene. Specification 547,730 is referred to.